Process of coloring iron and steel black



WILHELM U'rENnoaEEa, or corneas, GERMANY.

race or concerns No Drawing.

To all whom it may concern:

Be it known that I, WILHELM U'mNnon- FER, a citizen of Germany, and a resident of Cologne, in the Re ublic of Prussia, Germany, have invented certain new and useful Improvements in Processes of Coloring Iron and Steel Black, of which the following is a specification. I

a The object of my present invention is to provide a process by means of which articles of iron and steel may be quickly and cheaply colored black. To attain this end I subject said articles to a single-working operation in a moderately heated bath of a certain composition, into which bath the articles to be colored are introduced without any preparatory treatment, such as the removal of any fatty matter and the like. On leaving the bath said articles are'provided with a permanent black colored coating.

The bath employed for putting my new process into practice consists of dissolved salts resulting from the combination of nitro-phenols with caustic alkalies-as for instance of sodium, potassium, or ammonium to which solution are added allic acid and an excess of chemically comblned or of free alkali. Very strikin results are obtained when the dissolved sa ts consist substantially of sodium picrate resulting from the combination of trinitro-phenol with caustic soda, to which solution are also added gallic acid and free caustic alkali to such an extent that an excess of free caustic alkali remains. The presence ofv the gallic acid in AND STEEL BLACK.

Application filed February 15, 1922. serial No. 536,755.

This bath reaches its full active force, when it has been but moderately heated, for which reason the hardness and the elasticity of any article of iron or steel introduced into said bath does not sufl'er in any way.

posed of dissolved salts whichresult from combining alkali with nitro-pheriols, of gallic acid, and of an excess of alkali.

2. The process of coloring iron and steel black consisting in treating the articles to be colored black with a heated solution com posed of dissolved salts, which result from combining alkali with nitro-phenols, of gallic acid, and of an excess of free alkali.

3. The process of coloring iron and steel black consisting in treating the articles to be colored black with a heated solution com posed of sodium picrate, of gallic acid, and of an excess of free caustic alkali.

Signed b me at Cologne, Germany, this 21st day 0 January 1922.

WILHELM UTENDtlR-FER.

colored black with a heated solution com- 

